This invention generally relates to a pressure differential gage, and more specifically to a pressure differential gage especially well suited for, and to a method for, detecting the presence of noncondensible gases in a refrigeration system.
As is well known in the refrigeration art, the presence of noncondensible gases or vapors such as air in a refrigeration system in undesirable because such gases reduce the capacity of the refrigeration system and increase the amount of work that must be done by the compressor of the system. For this reason,, refrigeration systems are often monitored or checked for the presence of noncondensible gases. Prior art methods and apparatus for detecting the presence of noncondensible gases in a refrigeration system usually employ the principle that the total vapor pressure at a high pressure region of a refrigeration system is the sum of the partial pressures of the refrigerant vapor and the noncondensible vapors at that region.
These prior art arrangements typically involve measuring both the vapor temperature and the total vapor pressure at a selected high pressure region of a refrigeration system, for example in the compressor discharge line or in the condenser of the system. This measured temperature, of course, is the same as the temperature of the refrigerant vapor at the selected region of the refrigeration system, and knowing this refrigerant vapor temperature, a worker or mechanic can refer to a text or chart to determine the partial pressure of the refrigerant vapor at the selected region. The difference, if any, between this determined partial pressure of the refrigerant vapor and the measured total vapor pressure at the selected region of the refrigeration system indicates the presence and the amount of noncondensible gases in the refrigeration system.
While these prior art methods and apparatus are effective, they are somewhat time consuming, expensive, and cumbersome. In particular, they involve manual inspection of a number of gages, thus requiring costly manual labor. Also, they require reference to a text or chart which may not always be readily available or easily read.